Mode1 Interlaminar fracture toughness in unidirectional carbon-fibre/epoxy composites

High performance carbon fibre/epoxy composites, which are increasingly used for structural applications are susceptible to delamination. In response to this problem, the mode I interlaminar fracture toughness of unidirectional carbon/epoxy laminates has been studied under tensile loading by using a double cantilever beam (DCB) specimen. The fracture energy is deduced from the data according to the area and the compliance methods. The morphology was explained through thermal analysis using DMA and fractography from scanning electron microscopy (SEM). Results showed improvement in high temperature moulding compound (HTM) system with 180°C cure in terms of interlaminar fracture toughness. There is also an improvement in MTM and LTM systems. SEM micrographs revealed their excellent delamination resistance as good crack stoppers with the evidence of strong fibre/matrix interface. For MTM systems GIc values dropped after post curing. This reduction was significant for MTM49-3 but not so much in the case of MTM49-7 laminate. On the other hand, the GIc for LTM45-1 did not seem to be affected by post curing at elevated temperature.